1. Field of the Invention
This invention relates to joining means for rotor discs particularly such joining means in a durable configuration.
2. The Prior Art
In the compressor rotor of a gas turbine engine, there is at times, a need to repair or replace components thereof, e.g. rotor discs. Rather than replace all of the discs when one is damaged, the prior art has utilized replaceable, bolted-together, disc segments, per FIGS. 1 and 2 hereof. Thus per FIG. 1, disc 10, having flange 12, and disc 14, having flange 16, are fastened together through disc 18. That is, a bolt hole is drilled through disc flange 12, disc 18 and disc flange 16 and a bolt or stud 20 passes through the respective bolt holes and fastens the above components together, as shown in FIG. 1.
Per FIG. 2, discs 22, 24, and 26 are fastened together in a similar manner by bolt 28 and discs 26, 30, and 32 are fastened together in a similar fashion by bolt 34.
But the above indicated holes (for the respective bolts) are located in disc areas of high stress during compressor rotation, as indicated in FIGS. 1 and 2.
That is, FIGS. 1 and 2 show prior art bolted-on discs of earlier gas turbine engines which have become more susceptible to disc fatigue originating at the above bolt holes, as the RPM of newer gas turbine engines has increased.
Accordingly, the above prior art disc joining means are now less acceptable for newer compressors because of low cycle fatigue life limitations at the above disc bolt holes.
In other prior art are U.S. Pat. No. 4,576,547 to Weiner et al (1986) and U.S. Pat. No. 4,808,073 to Zaehring et al (1989). However, these references disclose means for cooling compressor rotor structures and are not directed to structural means to reduce local rotor stresses for increased durability thereof.
Accordingly, there is need and market for means for joining removeable rotor discs that avoids the above prior art shortcomings. There has now been discovered a configuration for joining rotor discs wherein bolt hole stress concentrations are located away from disc high stress areas.